将可选块或闭包传递给Swift中的函数 [英] Pass optional block or closure to a function in Swift

问题描述

将可选块传递给Swift中的函数的正确语法是什么？

What is the correct syntax to pass an optional block to a function in Swift?

推荐答案

作为Objective-C块语法，它远不是显而易见的。在此示例中， notConnected 参数是可选的：

Although not as hard to remember as the Objective-C block syntax, it's far from obvious. The notConnected parameter is optional in this example:

    func whenConnected(block: Void -> Void, notConnected: ((Void) -> Void)?, showErrorMessage: Bool) -> Void {

        let connected = Reachability.isConnectedToNetwork()

        if connected {
            block()
        } else {
            notConnected?()
        }

        if showErrorMessage {
            // your error handling //
        }
    }

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